In machines having top loading, hauling bodies it is desirable to provide a pivoting cover to retain the load in the body during travel of the machine. Otherwise, loads of material such as waste, grain, sand, dirt and other fine material tend to be blown from the body by air currents resulting from ambient winds, air flow due to the speed of the machine or both. This is objectionable due to loss of a portion of the payload as well as undesirable deposit of the material on the roadway and adjacent property.
Thus for various reasons closure means are desirable to prevent loss of material from open-topped truck bodies.
In currently known machines it is common practice to provide various covers or doors over openings in the body to retain the payload within the body during transit and until the operator is ready to dump the load. In most cases, however, the covers open automatically responsive to tilting of the body or must be opened by power means, such as hydraulic cylinders, to permit the payload to exit the body as it is pivoted to the dumping position. In many instances opening of the cover during dumping raises the center of gravity of the machine an amount sufficient to cause instability of the machine. This change in the position of the center of gravity may contribute to an overturning moment if the machine is on a side incline or is moving as the load is being dumped.
U.S. Pat. No. 2,941,682 issued Jun. 21, 1954, to C. R. Keys, U.S. Pat. No. 3,913,969 issued Oct. 21, 1975, to N. R. Hoch, USSR Patents 1,268,448 issued Nov. 7, 1986, and USSR Patent 281,057 issued Dec. 3, 1970, show various dump bodies having covers associated with openings therein. In all of these instances it is indicated that the covers must be in an open position when the body is tilted for dumping of the load therefrom.
Thus it is desirable to provide a dump body having a cover which may remain closed when the body is tilted for dumping. This maintains a relatively low center of gravity of the machine to enhance stability of the machine when the body is tilted for dumping of the load. It is also desirable to maintain a relatively low center of gravity during a top loading exercise during which the cover must be open.